Internal filter



FIG. 1 is a perspective view of the internal filter showing my new design;

FIG. 2 is a front plan view thereof;

FIG. 3 is a back plan view thereof;

FIG. 4 is a right plan view thereof;

FIG. 5 is a left plan view thereof;

FIG. 6 is a downward plan view thereof; and,

FIG. 7 is an upward plan view thereof. 

CLAIM The ornamental design for an internal filter, as shown and described. 